A simple analysis of squeeze films between compliant surfaces is presented and supported experimentally. Application of this analysis to synovial joints strongly indicates that a squeeze film of synovial fluid is readily maintained; further, the film appears to be hydrodynamically replenished through entrainment of fluid when the joint is moved. Joint failures due to ageing or injury and the failure of prostheses are rationalizable in terms of reduced film thickness and increased stress resulting from reduction of conformity and compliance of joint surfaces.
B oundary lubrication by hydrocarbon s was explored by usin g a four-ball mach ine with 52100 steel specimens at 0.35 em per second slidin g veloci ty. The chemi cal type of the hydrocarbon and the am ount of oxyge n dissolved in it appeared important. Low molecular wei ght liquid aromatic hydrocarbons exposed to ambient air w ere found as effective as straight mineral oils in controlling wear , while saturated hydro carbons usually w ere markedly poorer . Benz ene and cycloh exane were used as m odel lubri cant s in the study of oxyg en concentration in vapor and liquid phase. Both high and low oxyge n-to-hydrocarbon ratios favored high wear and inor ganic wear products. Certain in term ediat e rati os favored low wear and the formation of an oxy genated organic "friction poly m er" w hich prevent ed metallic cont act. Re sults are discussed in the light of kno wl edge concerni ng catalyt ic reactions at clean metal sur faces.
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